1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device and the driving method thereof that is adaptive for improving a visual picture quality by changing the buffering location of analog data voltages, which are supplied by the unit of one horizontal line, for each fixed period.
2. Description of the Related Art
A liquid crystal display device controls the light transmittance of liquid crystal cells in accordance with video signals to display a picture. And, an active matrix type liquid crystal display device where a switching device is formed for each liquid crystal cell is advantageous in realizing motion pictures because the switching device can be actively controlled. The switching device used in the active matrix type liquid crystal display device is mainly a thin film transistor (hereinafter, referred to as “TFT”), as in FIG. 1.
Referring to FIG. 1, an active matrix type liquid crystal display device converts digital input data into analog data voltages on the basis of a gamma reference voltage to supply to data lines DL, and at the same time, supplies scan pulses to gate lines GL to charge liquid crystal cells Clc therewith.
The TFT includes a gate electrode connected to the gate line GL, a source electrode connected to the data line DL and a drain electrode connected to one electrode of a storage capacitor Cst and a pixel electrode of the liquid crystal cell Clc.
Common voltages Vcom are supplied to a common electrode of the liquid crystal cell Clc.
When the TFT is turned on, the storage capacitor Cst is charged with the data voltages applied from the data line DL, to fixedly maintain the voltage of the liquid crystal cell Clc.
If the scan pulses are applied to the gate line GL, the TFT is turned on to form a channel between the source electrode and the drain electrode, thereby supplying the voltage of the data line DL to the pixel electrode of the liquid crystal cell Clc. At this moment, the liquid crystal molecules of the liquid crystal cell Clc are changed in arrangement by the electric field between the pixel electrode and the common electrode, thereby modulating the incident light.
The liquid crystal display device of the related art having the pixels with such a structure includes a data drive circuit which converts the digital RGB data supplied from a system into analog RGB data voltages to supply to sub-pixels.
Herein, a data drive circuit 100, as shown in FIG. 2, includes a plurality of output buffers 110-1 to 110-m which buffer the converted analog RGB data voltages to supply to each sub-pixel. Herein, the output terminals of the output buffers 110-1 to 110-m are connected to correspond to a plurality of output channels 120-1 to 120-m in a one-on-one relationship, respectively.
And, the output channels 120-1 to 120-m correspond to the data lines DL1 to DLm in the one-to-one relationship, respectively. To the data lines DL1 to DLm are connected the sub-pixels which are disposed on the same vertical line. Each pixel is formed of three sub-pixels, i.e., R sub-pixel, G sub-pixel and B sub-pixel, which are disposed on the same horizontal line.
The analog data voltages buffered by the output buffers 110-1 to 110-m are supplied to each sub-pixel through the pertinent data line for each one horizontal line. For example, the analog R data voltage buffered by the output buffer 110-1 for each one horizontal period is supplied to the R sub-pixel connected to the data line DL1 for each one horizontal line.
Because the analog data voltage is supplied to each pixel through the output buffers 110-1 to 110-m, if an offset error is generated in the first output buffer 110-1 such that the gray level of the R data supplied through the first data line DL1 becomes higher or lower than a desired gray level in the buffering process of the output buffer 110-1, then the gray level realized in the sub-pixels on the same vertical line connected to the first data line DL1 becomes darker or brighter than the gray level realized in other sub-pixels of the pixel to which itself is belong, as shown in FIG. 3.
As in FIG. 3, in case that the vertical line is divided for each sub-pixel, if the gray level realized on one vertical line is continuously displayed to be darker or brighter than the gray level on another vertical line, then a user visually feels the gray level which is realized abnormally on the first vertical line.
That is to say, the liquid crystal display device of the related art has a problem in that the picture quality visually felt by the user becomes worse, as described above in reference to FIG. 3, if the offset error is generated in at least any one output buffer of the output buffers 110-1 to 110-m. 